Problem on COLD RESTART in Mervis

[ayone]

Hi, all .
I made a simple sequent task in FBD just flag three bool variables b1, b2, b3 in a row.
Duration of each task activated is 15sec.

It worked fine except after Cold restart on mervis.
On what happen is b2 and b3 activated on same time. It seems F_TRIG was activated even though I set each variables FALSE as initial value connected to F_TRIG. I appreciate if someone tell me why it happened and point me out the problem of my code.
Sorry for pics, I could not figure out how to upload my project here.

Thank you.

ayone

, timer counts on same time.